1. Field of the Invention
The present invention relates to an image processing technique for converting a bit-map image having a plurality of colors into vector data.
2. Description of the Related Art
Paperless offices are now becoming common as environmental problems draw more attention. Image processing systems capable of achieving a paperless office system are now becoming commercially available. For example, in one system, a scanner is used to scan paper documents, and then the scanned data is converted into portable document format (PDF) for storage. An example of such a system is disclosed in Japanese Patent Laid-Open No. 2002-91949 (corresponding US patent Application Publication No. 2002/0087602 A1).
Japanese Patent Laid-Open No. 9-289586 (corresponding U.S. Pat. No. 6,389,162 B2) discloses another system. To enhance the efficiency of encoding in the transmission and storage of image data, noise occurring in the background of an image to be processed is removed, and the color of characters and figures is automatically quantized. The characters are then character coded in optical character recognition (OCR), and the figures are vectorized. This technique disclosed in Japanese Patent Laid-Open No. 9-289586 enhances the coding efficiency of an image by automatically quantizing color.
However, a user may wish to extract only a desired colored portion of an image for efficiency purposes. It is known that many conventional image processing systems are unsuitable for this task.
For example, the user may wish to first scan and reuse an examination sheet that has been graded or corrected with a red pen. The problem and answer sections of the examination sheet will typically be marked-up with the red pen. To reuse the examination sheet data, the problem portion must be extracted without the answer section and without portions marked-up in red. If the image is merely segmented into rectangular area for each object, the problem and marked-up section are extracted together without separation.